On Don Kendall's roadster...what tire pressure should I be running? I've done a bunch of research but can't seem to find the answer...currently I have 25lbs front & back:
Those recommended air pressures don't take the weight of the car into account. I run 27psi in mine. so I think 25 is probably pretty close to ideal on your roadster. Just check the wear patterns and adjust accordingly.
Nope...first place I looked. All it says is "Max pressure" which is 35#'s on the fronts and 41#'s on the rears...which we all know would be insane.
25 is a good starting point. I run 28 front and 26 rear in mine, that seems to be the best for ride and handling in my car, but you will need to fine tune yours to end up with the best one. What I do is I keep adding a couple of pounds of pressure until the ride starts feeling bouncy or harsh then I back off to where it feels good again. The reason I run more in the front is the engine end is heavier. Don
Here is what I have done since first seeing it here on the HAMB several years ago. A perfectly inflated tire will gain 4 lbs after driving a few miles. This was based on something this guy had read from Michelin, so I don't know if it applies to bias ply. So if your tire gains less than 4 lbs it is overinflated, and if it gains more than 4 it is underinflated. I have followed this since seeing it and it seems to be true.
Thanks guys...these are radials and I was told 24 in the front and 26 in the rears so I'm just splitting the difference...this car certainly doesn't weigh very much so I just wanted to see what you guys...the experts thought.
I'm thinking all hot rods are different. I played with mine, until I found what works. I also try to keep my gas tank full. My T Bucket rides better with a full tank over the rear end. I think you might try good old trial and error. Gives you an excuse to do a lot of test drives.
Okiedokie.Not doubting-tires do gain pressure from heat I just don't get the +- 4lbs variance as opposed to +4 is proper inflation.
You are on the right track you might have to play with it a bit for best ride quality, handling and tread contact with the pavement. You might want to check the tread contact by either rolling it over some water and then across smooth dry cement so you can see what the tread contact is. Too little air is going to wear the outside edges (both) more than the center while too much air will cause the center to wear more than the rest of the tire. I saw a lot of the wear in the middle when guys started buying radials in the 70's and then didn't like the beer belly look with the correct air pressure in them so they aired them up until they "looked right" or the way they wanted them to and only about an inch and a half of the center of the tread was carrying the weight of the car.
Most tire manufacturers have a tech line. If you call them, and give them rim width, tire size, and the weight of that end of the car, they will give you the ideal pressure. I have done this several times with good results.
Sweet ride! Ive used this method on my old jeepster when increasing tire size Let the chalk tell you You can also “calculate” your tire pressure with the chalk method. This involves coloring a section of your tire with chalk to see how much tread is making contact with the ground. Start by finding a flat road surface. Concrete is actually the best choice, but you can also do this on asphalt. Make a mark with soft chalk that goes all the way across your tread. Then, gradually drive your truck forward about 50 feet and then backwards 50 feet. Analyze the chalk on the tire. If the chalk is only worn off on the center of the tire, reduce the tire pressure slightly and go through the process again. With the adjustment, you should see the chalk wear off more broadly. Keep making tiny adjustments in the tire pressure until the chalk wears off evenly and all the way across the tread. You will have to complete this process for each of your four tires. Once you’ve found the right street pressure, add 10% to all four tires. Then, measure the tires and add pressure to balance them. As explained above, you need to measure from the wheel to the ground. Start by balancing the profiles of the front tires with each other. Then, balance the front tires again with the rear tires. Always adjust the tires with the smaller profiles by adding air. The advantages and disadvantages of this method are the same as those involved in the second method above. If you go through the process correctly, you end up with the ideal tire pressure. But, this method is tedious and there’s a reasonable chance that you will make a mistake. Posted using the Full Custom H.A.M.B. App!
BGII, my '31 "A" roadster w/sbc, has 5,60X15 bias ply on front, and 8.20X15 bias ply on rear. And I run 24# in front and 12# in the rear. It all depends on tire size, weight per tire, rim width, and tire construction, radial or bias. The chalk method above will go a long way towards helping you find what pressure you need. Another good way is the laser aimed infra-red temp guns you can get so cheap now, although the faster acting ones are a little more expensive, but give a quicker reading. My son and I used one to great advantage in modified competition go kart oval racing on dirt. He would make some hot laps, then pull off the track into the pits where I took temps of each wheel inside, center, and outside of tread width of the slicks. I yelled out the readings to an assistant who wrote them down in a much rehearsed sequence. We took those numbers and surmised which edge of which tire was working too hard and worked on tire pressures and wheel offset and loading o compensate. I'm setting up a pair of slicks for the rear of BGII for drage only, and intend to use this method to figure out tire pressure.
about I would run 3/4 side wall pressure, 1/2 is ok but not recommended for long haul due to excess belt heat , the formula I used to use was take the max tire weight listed and divide by the psi listed then figure ( example 1499 per tire @44 psi ( 205/70/15) 44 ÷1499 = .0293529 ( I round up to next whole ) ( .03 ) psi per load pound then the load on the tire is 750 pounds ( 1500 total per axle ) so take that and then take that sum and multiply it by the psi per pound 750x.03 =22.5 and often it was pretty decent , but one thing to watch for is cupping as a radial tire will cup out across the tread if the pressure is to low , every 100-200 miles run your hand across the tread and if you feel cupping or hear a thumping or skipping sound ( the ticking sound you hear from truck trailer tires when you pass them as they are often undampened ) up the tire pressure as cupping is a sign of excessive tread/tire drag just up the pressure 2-3 psi . one thing to consider Ford was running the flipping exploders front axle at 26 psi on a 44 psi tire ( 225-235 /70/15) and the load was close to 2200+ pounds on the front axle ( ship weight was 4190 ) . they went to 30 psi after the lawsuits when by calculation it should have been 32 psi . and it was done all for comfort . if you scale your cars axles (your going to need to know the axle weights and it can be done at a cat truck scale for $10 or grain elevator or sand yard and talk to the scale master before pulling on the scale, and explain you need axle weights ) and then call your tire manufactuer ( unless its a odd brand made over in asia except kuhmo ) as for the tech people and they should be able to tell you what the safe psi rating is .
Thanks guys for all the great info...I knew you guys would have the answers. I generally keep as close to a full tank as I can and from what I can tell,the tires are all wearing evenly. If I go over a pretty good bump,the rear end will bounce around quite a bit so that's why I think less pressure there is a probably to my benefit for a smooth ride.
A little O/T but I have a new Silverado pickup with all the goodies the sticker on the drivers door says to inflate to 32PSI for the tires the factory put on the truck. After a few miles down the road the computer screen that monitors them says the fronts are at 35PSI and the rears are at 34PSI. So they definitely gain pressure as they warm up.
Timely thread. I put some skinny bias ply tires on my Chevy II. Fronts are 6.00-15, rears are L78-15. The front rims are bit too wide, they're 5 inches, but soon to be replaced with 4.5". Right now I'm running 32 front, 25 rear. Car weighs about 2700 empty, and with the altered wheelbase, the front/rear distribution is probably pretty close, although I still need to weigh each end to find out. The handling at highway speeds is a bit sensitive, especially to wind. Ideas?
Ive found the pressures vary a lot. The out side temp. Around here when its 100 degrees out the asphalt can be 180 degrees and on a long drive it builds up a bit more air pressure. My model a would start to get a wheel bounce on long drives that wouldn't be there earlier. When i checked the tire pressure my 31 had turned into 36-38. But in colder weather its a little different. Now i think i run 26 in the front.
Let's say your tire is inflated to 25 psi. If it gains 4 psi to give you 29, then that would be the correct inflation for the tire on your car. If it gained only 1 psi, that would indicate the tire should have been inflated to 22 psi. If it had gained 6 psi that would indicate a correct inflation would be 27 psi. Make sense? I have no scientific evidence to support this, but it "feels" right to my butt.
if the pressure goes up a lot that means the tire is working too hard , on semis loaded the pressure will often go up 10 psi on a 70* day but 25-30 on a desert highway , but thats because they have alot of flexing to do because of the weight .. ( and heat asorbed from the pavement ) remember expansion is caused by heat which means work or absorbsion , also if the ass end is hopping it could mean your rear spring rate is too high ( stiff made for a heavier car ) or your shocks have the wrong bias to them ( too much compression and not enough extension . ) this is were adjustable shocks are nice as you can change the dampening rates , my pick up does this due to the heavy spring pack it uses in the ass end and the gas shocks , If I want a smooth ride I have to put 1-300 pounds in the bed over or behind the axle to make it ride nice . but it was built to haul stuff not comfort , thats were the wifes car comes in . and squirell half your problem is your a billboard in the wind , driving that thing is like driving a lifted Jeep gonna be hairy with a center of gravity around your nose ....
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